Fenestrated bone graft

ABSTRACT

The present invention relates to a fenestrated bone graft and a method of preparing cortical bone in thin strips then fully demineralizing it to give it formed flexibility and then creating fenestrations in the cortical bone in a fashion similar to but not identical to skin grafts.

RELATED APPLICATIONS

The present invention is a division of co-pending U.S. application Ser.No. 14/556,492 filed on Dec. 1, 2014 entitled “Fenestrated Bone Graft”.

TECHNICAL FIELD

The present invention relates to a fenestrated bone graft and a methodof preparing cortical bone in thin strips then fully demineralizing itto give it formed flexibility and then creating fenestrations in thecortical bone in a fashion similar to but not identical to skin grafts.

BACKGROUND OF THE INVENTION

A bone graft is a surgical procedure used to fix problems associatedwith bones or joints. Bone grafting or transplanting of bone tissue isbeneficial in fixing bones after trauma, degenerative damage, problemjoints, or growing bone around implanted devices, such as total kneereplacement or spinal implants. The bone used in a bone graft can comefrom the patient, from a donor, or could be entirely manmade. Onceaccepted by the patient, the bone graft provides a framework where new,living bone can grow. The two most common types of bone grafts areallograft: this graft uses bone from a deceased donor or a cadaver thathas been cleaned and stored in a tissue bank and autograft: graft madefrom a bone inside a patient's body, such as the ribs or hips. The typeof graft used depends on the type of injury the surgeon will berepairing. Allografts are commonly used in hip, knee, or long bone (armsor legs) reconstruction. The advantages are that (a) there's noadditional surgery needed to acquire the bone, and (b) it lowers therisk of infection since additional incisions or surgery on the recipientwill not be required. Bone grafting is done for numerous reasons,including injury and disease. There are four main reasons bone graftsare used: fractures, a bone graft may be used in the case of multiple orcomplex fractures or those that do not heal well after an initialtreatment; fusion, most often done in the spine, fusion helps two bonesheal together across a diseased joint; regeneration, used for bone lostto disease, infection, or injury, this can involve using small amountsin bone cavities or large sections of bones; and implanted devices, agraft can be used to help bone heal around surgically implanted devices,like joint replacements, plates, or screws.

All surgical procedures involve risks of bleeding, infection, andreactions to anesthesia. Bone grafts carry these and other risks,including: pain, nerve injury, rejection of the bone graft andinflammation. The surgeon typically will make an incision in the skinabove where the graft is needed. He or she will then shape the donatedbone to fit the area. The graft will be held in place using variouspins, plates, or screws.

The present invention provides a new and improved type of bone graft anda method of manufacturing the graft to facilitate improved implantationtechniques.

SUMMARY OF THE INVENTION

The present invention relates to a fenestrated bone graft and a methodof preparing cortical bone in thin strips then fully demineralizing itto give it formed flexibility and then creating fenestrations in thecortical bone in a fashion similar to but not identical to skin grafts.

The advantage of this new allograft is it provides a unique way todevelop ingrowth through the fenestrations. The strips can be cut up to30 cm so they can be used for lateral lumbar fusions or even multiplefusions in the thoracic and lumbosacral spine. The graft can also berolled into a construct that can be used inside of a cage. Theflexibility also allows for the ability to create different shapes suchas a tube or a basket that can contain either allogeneric or autogenericbone graft material with or without stem cells. The fenestrated bonegraft is relatively inexpensive and easily scaled. The fenestrated bonegraft is a device in which there are created fenestrations which allowfor the use bone sutures, suture material made from the same bone thatcan be used to weave the openings in the fenestrated graft to create avariety of shapes like a cylinder, a basket, a wedge or a roll.

Preferably, a fenestrated cortical graft has an allograft bonestructure. The allograft bone structure has an exterior or outer surfaceand an interior or inner surface. The structure is fenestrated with aplurality of pores or openings extending through from the exterior orouter surface to the interior or inner surface to form open passages.The allograft bone structure can be formed as a flat sheet.Alternatively, the allograft can be formed as a tubular or cylindricalshaped graft. The allograft bone structure is preferably made pliable.The pliable allograft bone structure is conformable to flex about thesurface of a damaged bone to provide a fenestrated cortical bone graft.

Definitions

As used herein and in the claims:

“BMA” refers to Bone Marrow Aspiration, a technique used to obtain theblood-forming portion (marrow) of the inner core of bone for examinationin the laboratory or for transplantation.

“Costal cartilage” refers to the cartilages that connect the sternum andthe ends of the ribs; its elasticity allows the chest to move inrespiration.

Demineralized bone matrix (DBM) is an osteoconductive and osteoinductivecommercial biomaterial and approved medical device used in bone defectswith a long track record of clinical use in diverse forms. True to itsname and as an acid-extracted organic matrix from human bone sources,DBM retains much of the proteinaceous components native to bone, withsmall amounts of calcium-based solids, inorganic phosphates and sometrace cell debris. Many of DBM's proteinaceous components (e.g., growthfactors) are known to be potent osteogenic agents. Commercially sourcedas putty, paste, sheets and flexible pieces, DBM provides a degradablematrix facilitating endogenous release of these compounds to the bonewound sites where it is surgically placed to fill bone defects, inducingnew bone formation and accelerating healing. Given DBM's long clinicaltrack record and commercial accessibility in standard forms and sources,opportunities to further develop and validate DBM as a versatile bonebiomaterial in orthopedic repair and regenerative medicine contexts areattractive.

The term “Fenestration” means openings in the walls of a structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 shows 15-20 cm cortical demineralized graft with fenestrations,Freeze dried. Clinical usage for long segment fusion, segmental defectsas a wraparound intramedullary implant.

FIG. 2 shows Rib with fenestrations. Clinical indications, cranio andmaxillofacial surgery, spinal cage filler (can add micronized bone, dBM,MIAMI cells) to intact center.

FIG. 3 shows Demineralized rib; higher power magnification demonstratingfenestrations and cortical architecture.

FIG. 4 shows a fenestrated graft strip formed into a basket shape.

FIG. 5 shows a fenestrated graft strip formed into a basket held by asurgeon.

FIG. 6 shows a fenestrated graft strip formed as a pouch or pillowstuffed with a biologic material or stuffing to promote new bone growth.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 2 and 3, the original concept of fenestratingdemineralized cortical bone was developed in the rib 100 and the rib 100was an ideal graft because it can essentially be demineralized andcreates a large wide flat surface. After removal of the minimalcancellous center, the rib 100 is passed through a press with cutting orpunch blades that create fenestrations or openings 12 bounded byinterconnected bone struts 14 that gave the fenestrated bone graft 10 aporosity as well as stretchability and flexibility to fit intorelatively defined spaces. The actual processing of the rib graft wasdone aseptically and used no alcohols, peroxides or decontaminationsteps in its recovery. In doing so, the clinicians removed all of thecostal cartilage that they used for other applications and distribution.They cut the rib 100 at ends 15, 16 into relatively long segments atleast greater than 8 cm. Following that, they treated the graft for apredetermined time in 1N HCL (one normal hydrochloric acid)(20-50parts/gram) ranging from approximately 1-3 hours continuously inspectingthe graft rigidity. Once they were satisfied with the texture andflexibility of the graft 10 they washed it in a washing solution ofPhosphate buffered saline approximately 20 minutes. Then they cut therib 100 longitudinally to maintain its cylindrical configuration. Thiscut along the length allowed for either using the graft as a flatconstruct or it could maintain the graft 10 in a cylinder. Thefenestration portion of the graft 10 is cut into the rib 100 and createdusing an in-house made bone cutter. Once the fenestrations or openings12 were made in the graft 10, the graft 10 was freeze dried using anovernight cycle and then packaged sterilely for clinical use in a peelpouch. Following the removal of the graft 10 from the plastic peel pouchit can be reconstituted in saline or lactated ringers with or withoutantibiotics for clinical applications. The graft 10 could be refoldedinto a cylindrical configuration and filled with either autologous orallogenic bone graft with or without stem cells moreover the graft 10could be rolled or folded into a confined space such as a cage or rolledinto a cylinder where it could be used for the application of satisfyinga short close open segment defect. The graft 10 could also be onlaidinto a vascularized myo-osseous pouch for the purpose of long segmentfusions in the spine, the thoracic or lumbosacral spine.

The tibial graft 20, as shown in FIG. 1, was conceived to create longersegments of bone for very long segment fusions in the case of scoliosisor a multi-segment instability or trauma of the spine. Again the graft20 was recovered from a tibia 200, in aseptic fashion without the use ofperoxides detergents or secondary decontamination steps. Secondarysterilization could however be employed if cultures were positive fornon-exclusionary organisms as outlined in FDA guidelines. Asepticcleaning in the processing state has been reinstituted and the tibiagraft 20 was cut on a band saw in a coronal fashion in lengths 10 cm orgreater, while the thickness is approximately 0.2 to 1 mm. The graft 20was then placed in a large graft cylinder and treated with 1N HCL (20-50parts/gram) for 4-6 hours with continuous inspection to assess therigidity and texture of the graft 20. Once the appropriate texture wasobtained, it was then washed in phosphate buffered saline three separatetimes for 20 minutes. The graft 20 was then placed on the bone cutter tocreate the appropriate fenestrations or opening 12 bound by theinterconnected bone struts 14 and then the tibia graft 20 was placed inthe freeze drier for an overnight cycle. It was then packaged sterilelyfor clinical use. In using the tibia graft 20, it was removed from thepeel pouch and reconstituted in saline or lactated ringers with orwithout the addition of antibiotics and then depending on the particularapplication, the tibia graft 20, like the rib graft 10 would be onlaidor folded into a cylinder or a roll or a basket into which particulategraft could be added along with a stem cell. FIGS. 4 and 5 show a basketformed from fenestrated graft 10, 20 strip folded over and laced orwoven together to form the basket shape. So the indications for thisgraft 20 are felt to be long segment fusion such as scoliosis,multi-level and trauma as well as maxillofacial surgery, surgeryinvolving defects in cranial pulp, or long segment defects as well asany other defect.

FIG. 1 is essentially showing a portion of a 20 cm long fenestrated bonegraft 20 that was derived from the tibia 200. It is freeze dried andthis is done after the fenestrations 12 were created in the graft afterit was fully demineralized. Once this fenestrated bone graft 20 ishydrated it resumes its pliable shape and can be formed into severalalterations that can retain smaller bone particulate graft and stemcells.

FIG. 2 shows a cylindrical graft 10 made from rib 100. One notes thatthe fenestrations 12 are created by not having to longitudinally sectionthe rib 100, but using a more robust cut to create fenestrations 12throughout the graft 10. This is a very interesting graft because it canbe filled with allograft bone particulate graft or dbm or stem cells ora combination thereof and can be sewn or restricted above and below atends 15, 16 of the rib graft 10. This construct can be used to fill acage construct or potentially to augment a segmental defect or tosatisfy a defect in the portion of a long bone or a strip in a pelvis.

FIG. 3 is a higher power magnification showing the morphologic changesthat are created in the demineralized cortical bone followingfenestration. One notes the uniformity and openness of porous bonestructure and the intervening connective strut structure 14 of corticalbone.

The desired texture is a surface related property that has to do withthe pliability and stretchability of the grafts 10, 20 themselves. Ithas to be sufficiently demineralized to have the flexibility whichallows creating a variety of different shapes. If too stiff, obviouslyit can't create these shapes, if demineralized it too much it loses someof the inductivity that is inherent in demineralized bone.

The cut openings 12 or fenestrations 12 are made with a punch press withcutting blades. As shown, these cutting blades create slits that canform openings 12 that are oblong by stretching the graft. One can makethe openings 12 any size desired. To entrap bone particles calls forpore sizes that are small. This will restrict micronized bone and onecould see that these are grafts 10 or 20 formed as strips having theactual pore size about 3 mm long and 1.5 mm wide for the fenestrations12. The bone connections or struts 14 or strut networks formed are about1 mm or less in diameter, width or thickness 0.8 to 1.2 mm, at theconnective portions, about double that. The actual sizes of thefenestrations 12 can vary in a range from fractions of a millimeter toseveral millimeters depending on the graft application, 0.2 mm to 5 mm.

This bone graft 10 or 20 could be used as a spacer in the mid-foot andor the fore foot, because of its pliability.

With reference to FIG. 6, the allograft bone structure 10, 20 can bemade in the form of a pouch or pillow 10, 20. It uses 100% humandemineralized cortical sheet. The pillow 10, 20 is meshed, perforatedbone with fibrous cortical cancellous stuffing 300. The stuffing 300 canbe cancellous bone material, autologous or allogenic bone graft, with orwithout stem cells, allograft bone particulate graft or dbm or stemcells, BMA or any combination thereof. The pillow ends 15, 16 can besutured. Cortical sheet is machine stamped for consistency in the openarea as previously discussed. It has flexible handling characteristicswith osteoconductive and osteoinductive properties. It is easy to handleand deliver, is pre-configured implant sized to the specific procedureand it aims to solve the common problems of graft site migration and theability to visualize the implant post-surgery. It can be made availablein multiple lengths. It has a 5 year shelf life at room-temperaturestorage and can be conveniently distributed in packs of 2. As shown, thedemineralized cortical meshed perforated “pillows” 10, 20 can beprocessed from donated human bone utilizing the previously discusseddemineralization technology; the grafts are flexible and featureosteoinductive and osteoconductive properties. When combined with BMA,it provides all of the necessary elements for bone regeneration. It isdesigned for posterolateral and cervical spine surgery applicationsincluding single- and multi-level fusions, as well as deformityprocedures. It can be distributed in packs of 2 to provide fusionmaterial for both sides of the spine, thus minimizing the number ofboxes to open during procedures. It can be provided in various sizes,for example: 20 mm×50 mm (2) for Posterolateral applications; 10 mm×100mm (2) for Spinal Deformity; and 10 mm×50 mm (2) for Posterior Cervicalapplications.

Variations in the present invention are possible in light of thedescription of it provided herein. While certain representativeembodiments and details have been shown for the purpose of illustratingthe subject invention, it will be apparent to those skilled in this artthat various changes and modifications can be made therein withoutdeparting from the scope of the subject invention. It is, therefore, tobe understood that changes can be made in the particular embodimentsdescribed, which will be within the full intended scope of the inventionas defined by the following appended claims.

What is claimed is:
 1. A fenestrated cortical bone graft comprises: atextured and flexible allograft bone structure, the allograft bonestructure being made from a single piece of long cortical bone of 8 cmlength or greater from a rib or 10 cm length or greater from a tibia,the rib treated in 1N-HCL for 1 to 3 hours whereas the tibia is treatedin 1N-HCL for 4 to 6 hours to texture the cortical bone and make pliableor flexible, the cortical bone being cut along a length of the bone andlaid flat in a flat sheet, the structure having an outer surface and aninner surface, the structure being fenestrated along a length of thebone structure with a plurality of cut slits sized to uniformly extendthrough from the outer surface to the inner surface to form a pluralityof open passages when the bone structure is stretched, the fenestratedcortical bone graft being freeze-dried and packaged sterilely forclinical use, the freeze-dried fenestrated cortical bone graft beinghydrated and reconstituted in saline with or without antibiotics orlactated ringers with or without antibiotics for clinical use to resumethe pliable or flexible condition of the freeze-dried fenestratedcortical bone graft, the open passages being bounded by aninterconnected network of bone struts defined by pairs of adjacentslits, each bone strut having a width of 0.8 to 1.2 mm that doubles atconnective portions, the bone struts in combination with the slitsgiving the hydrated and reconstituted fenestrated cortical bone graftstretchability and flexibility wherein the allograft bone structure isformed as the flat sheet, the flat sheet of the allograft bone structureis made pliable and conformable by the treatment in 1N-HCL which alsodemineralizes the bone allowing the flat sheet to be formed intodifferent shapes, wherein the bone allograft structure has a thicknessof 0.2 mm to 1 mm as measured from the inner surface to the outersurface and wherein the structure when stretched has the slits opened,the slits being sized in length allows the open passages to be of anoblong shape in the range of 0.2 mm to 5 mm when the sheet is stretchedand the plurality of slits are configured by cutting through the flatsheet using a bone cutter with cutting blades, cutting fenestrations inthe flat sheet which open when the flat sheet is stretched, wherein eachslit is of a length prior to stretching and the openness of each of theslits varies dependent on the amount of stretch on the fenestratedcortical bone graft.